Nymph in folklore, a dryad (5)
I believe the answer is:
oread
'nymph' is the definition.
(thesaurus)
'in folklore a dryad' is the wordplay.
'in' says the answer is hidden in the clue.
'OREAD' is hidden in the letters of 'folklore a dryad'.
(Other definitions for oread that I've seen before include "classically beautiful girl" , "Maid of the Mountains" , "spirit at peak?" , "O dear, a strange mountain nymph" , "mountainous girl" .)